Upgrades to ViNERS plot code, models and function documentation

+mesh/get_perineurium_thickness.m

+mesh/insert_gmsh_electrodes.m

+mesh/insert_gmsh_fascicles.m

+mesh/make_gmsh_thinLayer.m

+mesh/mesh_quality.m

+models/ECAP_recording.m

+models/Sundt2015_v1.hoc.template

+models/Tigerholm2014_v1.hoc.template

+models/analysis_interface.hoc

+models/axon_model.m

+models/axon_population.m

+models/axon_sfap.m

+models/axon_thresholds.m

+models/compose_waves.m

+models/electrode_array.m

+models/make_fascicles.m

+models/membrane_currents.m

+models/nerve_anatomy.m

+models/nerve_recording.m

+models/nerve_stimulation.m